1. Field of the Invention
This invention is a method of compressing molding sand and an apparatus for compressing molding sand. More specifically, this invention is a method of compressing molding sand by blowing compressed gas through a plurality of compressed gas conductors onto the entire surface of molding sand inserted within a molding frame that is separated from a model but that encloses its sides. The frame and the model are both placed on a molding plate that is provided with a vent for exhaust.
2. Background Information
Many methods and apparatuses in this technical field are publicly known. For instance, EP No. 0263977 teaches a device in which molding sand inserted within a molding frame encloses a model from its sides, and to compress the molding sand a squeezing device is provided above the molding frame, the squeezing device and the molding frame being complementary to each other, said squeezing device comprising a plurality of squeezing members and compressed gas pipes.
In that device compressed gas is blown onto the molding sand at a uniform flow rate through compressed gas pipes so that the gas is simultaneously blown onto the molding sand through all compressed gas pipes of the squeeze device and flows into the sand. Then the molding sand is pressed mechanically by the squeezing members. In this way the mold is compressed uniformly within the molding frame.
But by using the above prior art, especially when forming a mold using a model consisting of sections with a great difference in their heights, compressing the higher sections and lower sections of the model to give a mold that precisely conforms may cause a part of it, e.g., a protruding part of it that corresponds to a pocket section of the model, to break during the time the completed mold is released from the molding frame after the compression is over.
This invention is designed to overcome such a problem. This invention aims to provide a method and an apparatus to compress molding sand so that different parts of the mold are compressed independently from the other parts and to minimize the energy consumed for compressing molding sand.